The debate -- a few initial observations
At least one major Florida paper, the Orlando Sun-Sentinel, has also made a major issue of Rubio's neglect of his Senate job, and Rubio's own bluntly-stated disgust with the Senate opened him up to this line of attack (the best proof of Jeb!'s ineptitude as a politician as that he didn't mention this during his initial attack). Bush seems to have a deep sense of entitlement and is the heir-apparent of a family which seems to think of itself as the royalty of the Republican party; he's not going to drop out of the race easily, and he still has considerable resources.
There are other lines of attack available against Rubio. His youthful appearance and lack of experience are ongoing concerns (one Republican blogger observed that a debate between him and Hillary would look like a schoolboy arguing with the teacher). His earlier support for illegal-alien amnesty still deeply rankles many Republicans. His opposition to abortion rights is radical even by Republican standards, something Hillary has already targeted him for and which she could use in a general election to accurately paint him as a dangerous extremist. These are not points that Jeb! himself could easily use against him -- but surrogates and PAC ads could, and the Bushes know how to fight dirty. Even before this debate, Jeb! viewed Rubio as his most dangerous opponent -- hence the misfired attempt to torpedo him yesterday. He'll be even more of a target now.
Some Republicans seem to feel that arch-wingnut Ted Cruz was a standout at the debate, though it's hard to see how a man loathed by his own party's establishment (and fellow Senators) can win, unless everyone else self-destructs.
The demolition derby isn't over yet. There are still fifteen of these wheezy old clunkers rattling around a rather small arena, some of them still convinced they can win the prize if they can just total out whichever other of their number looks least decrepit. Hopefully they'll all end up at the junkyard.